Metal seat assemblies employing metal seals are particularly desirable for high temperatures and high pressures. Usually a valve is subjected to a high temperature environment as it is transporting a lading at a relatively high temperature which is considered to be any temperature above around 300.degree. F. It is desirable that the metal seals be sufficiently flexible to maintain a fluid-tight seal with a movable valve member when the valve member is in a high temperature service.
Metal seals have been employed heretofore for high temperature service in ball valves such as shown in U.S. Pat. No. 4,071,220 dated Jan. 31, 1978. This patent shows a metal seat having an inner annular groove to provide a flexible sealing lip with a metal spring in the groove to urge the metal sealing lip into engagement with the adjacent sealing surface of the movable valve member. Copending application Ser. No. 877,592 filed Feb. 13, 1978 entitled "Metal Gate Valve Having a Flexible Front Lip Face Seal" shows a metal seat member for a gate valve in which a flexible front lip face seal is provided by a flexible lip having an annular groove behind the lip so that the lip can deform to compensate for deformation of the valve body for maintaining sealing contact with the gate member as the valve is in the open and closed positions. This metal seat is particularly adaptable for high temperatures and high pressures.